With reduction in size of devices, a SOI field effect transistor is widely used in the industry with its advantages such as an excellent subthreshold swing, a small leakage current, and an effective suppression of a short channel effect and so on. Furthermore, in order to reduce series resistance of source/drain and further improve device performance, there has been a growing attention on a SOI field effect transistor having a schottky source/drain.
On the other hand, however, the SOI field effect transistor has a limitation on the performance of the device to some extent due to a self-heating effect thereof. For a bulk silicon field effect transistor, the heat generated in the device is substantially dissipated through a bulk silicon substrate. However, the SOI field effect transistor has a thick silicon oxide layer (generally in order of hundreds nanometers). Since the thermal conductivity of silicon oxide is only 1.38 W/m/K at room temperature, which is much smaller than that of the bulk silicon, the heat dissipation from a channel to the substrate is hindered. Furthermore, the SOI field effect transistor includes a very thin silicon film, where the thermal conductivity of the silicon film is smaller than that of the bulk silicon due to a surface phonon scattering, thus resulting in the heat dissipation is further suppressed. Therefore, as compared with the bulk silicon field effect transistor, the SOI field effect transistor has a significant self-heating effect, which adversely affects the electrical performance and reliability of the device. In order to reduce the self-heating effect of the SOI field effect transistor, one method, in which a heat dissipating layer with high thermal conductivity (such as graphene) is added onto a buried oxide layer so that the heat is dissipated through lateral sides, is adopted. Moreover, another method is that, a STI region is filled with a material with high thermal conductivity (such as diamond), and the STI region is extended to pass through a buried oxide layer and contact with a silicon substrate. In each of the above methods, since the heat dissipation structure is not connected to the device directly, the dissipation effect is poor.